I planned to post a big review, but I've noticed there are already a couple of more or less comprehensive reviews, so I won't re-invent the wheel, but rather talk about what other reviewers didn't mention.
I've been using this phone for 2.5 months now. All in all, it's a great phone with many features, but I will write about some of the annoyances:
1. You can't charge it with an USB cord, only the charger. I work a lot at the computer, so a charge from USB cord would be really handy.
2. When you lock the keypad, the dedicated music keys also get locked. When carrying in your pocket with keypad unlocked, some random numbers get pressed and possibly dialed, but you still want to be able to control the music player, without locking/unlocking the keypad everytime you want to switch a song.
3. The camera is reallyyyyy sloooow. But I don't take pictures with it, so it's ok. But just so that you know.

Everything else is very good. I listen to the music about 30 minutes everyday, talk about 5 minutes a day, don't take pictures, and don't play games, so with such usage, the battery lasts 5 days on mine, which is pretty amazing. I have read about strange clicking sounds between songs -- I have never heard them on mine, my firmware is v05.81. Also, the phone never hangs or restarts, as other people mentioned. The music quality is really good (I use Sony in-ear headphones). Even the picture quality is very decent (I only made a couple of test pictures). Although the spec talks about 4GB memory cards, I installed 8GB and it works just fine (the phone internally shows only 3.6GB, but it doesn't matter, it reads files from all 8GB). Well, if you have questions, just ask, I'll be glad to answer. Thanks!

sameer pathak, 13 Jun 2008it,s a good phone..but sound quality is not good.and plz can anybody tell can i change the sound plzupdate the software to version ( 5.81 ) the sound will be very loud and you will get timer during the call on display

I really liked it. slim, sleek, very handy and stuff but the speakers aren't all that good. and one more thing.. two months after i bought it, the caller cannot hear my voice coz the mic
in my handset doesn't work when i call.. it can record but i don't know.. when i call, people at the end of the line can't hear my voice. weird huh?. please tell me what i should do okay?. email- baby_blue_0x0@yahoo.co.in

I got this phone yesterday and so far have had nothing but good things with it. The locked T-Zone button from T-moblie bugs, but over all I like it. The speak is not amazing, but it is good enough to enjoy the music.

well to me this is the best Nokia phone I have ever used,I think its just perfect and I don't know why others are saying likewise maybe they should post reason. to be this is a very good phone with good sound quality, Thanks.

Anonymous, 14 Jun 2008omg this phone is " off da chain"
i origionally wanted a sidekick, but this phone has almos... morebest of the things come in small packages and 5310 is no exception. it may look fragile but strong enough to take few bumps.

dont you realize that the cameras are slow because its setting the pictures make it look better?
look at the bright side,when you take a picture at night, the picutures are brighter than any 2mpix cams..

will every person commonting on how crap this phone please shutup!i picked it up 2 weeks ago. it is great! it holds all the music i like and its given me no problems so far. everyone in my school is jealus of me having it. i think the sound is perfect. great phone X)

Actually I formerly owned the former Xpress Music Line (5200,5300 and the 5700) Actually these lineups we're great... until I met the 5310I was so excited what was hidden inside the box at first glance it was a union of the 5300 and the 6300 but to my suprise it was'nt really what I expected...... First of all the screen's backlighting cant even beat the 6300 nor the 5300.... The speakers whoa! slow down there.... The 6300 had a louder speakers than the 5310....The camera was tested...... Actually sad to say it was the worst 2.0 mp ever (slow and blurred).....
There are some positive things to talk about this phone...It can be expandable to up to 4gb....the music player has a new make up....A newer UI..... but all I can say is this if you are looking for a music player try the 5610 it works great....